One-piece roller-impulse member for timepiece escapement

ABSTRACT

A one-piece safety roller and impulse member for a timepiece escapement control is disclosed. The combination element is a low coefficient of friction engineering plastic and serves the control purpose of two separate elements heretofore used in the art of timepiece lever escapements to which this invention pertains.

United States Patent Cielaszyk 51 July 25,1972

[54] ONE-PIECE ROLLER-IMPULSE MEMBER FOR TIMEPIECE ESCAPEMENT [72]Inventor: Edward F. Cielaszyk, Oglesby, Ill.

[73] Assignee: General Time Corponflon, Phoenix, Ariz.

[22] Filed: Feb. 26, I971 [2]] Appl. No.: 119,265

[52] [1.5. CI. ..SB/l21 [51] Int. Cl. ..G04b 15/08 [58] FleldofSearch..58lll6R,l2lR,l22,140

[56] References Cited UNITED STATES PATENTS 3,335,562 8/1967 Schneider...58/l 21 R 3,469,392 9/l969 Tuetey Primary Examiner-Richard B.Wilkinson Asxistanr Examiner-Stanley A. Wal Attorney-Pennie, Edmonds,Morton. Taylor 8: Adams [57] ABSTRACT A onepiece safety roller andimpulse member for a timepiece escapement control is disclosed. Thecombination element is a low coefficient of friction engineering plasticand serves the control purpose of two separate elements heretofore usedin the art of n'mepiece lever escapements to which this inventionpertains.

2 Clalnl, 5 Drawing Figures ONE-PIECE ROLLER-IMPULSE MEMBER FORTIMEPIECE ESCAPEMENT BACKGROUND OF THE INVENTION Lever escapements arepredominately used in springwound clocks and watches. Common use is atoothed escape wheel connected through a gear train. The escape wheel ispowered from the well known mainspring or other power source. Anescapement lever pivoted about a point between its ends has at one end apair of pallet pins and at its other end a fork. The pins are separatedby a distance between the teeth of the escape wheel according to a wellknown formula. A balance wheel, biased by the usual hairspring, isarranged for oscillation on a balance staff.

As shown in the prior art (P10. 2) an impulse pin of hardened steel (orjewel) is fixed to the balance wheel. A safety roller of brass or thelike is fixed on the balance wheel shaft and is laterally separated fromthe impulse pin. The safety roller cooperates with the well known guardpin which is fixed in the escapement lever adjacent the forked endthereof. The indented or crescent portion of the safety roller allowsthe guard pin to pass freely when the escapement lever is unlocked,during oscillations of the balance wheel.

More specifically, the escape wheel, driven by the mainspring of thetimepiece through its gear train, forces the escapement lever to pivot.Consequently, the forked end of the escapement lever acts on the impulsepin, causing the balance wheel to rotate and increase tension of thehairspring. The tensioned hairspring then causes rotation of the balancewheel in the opposite direction. The escapement lever being held in itsbanking position due to the draft action between the pallet and escapewheel tooth, is positioned for entry of the impulse pin as the balancerotates. Due to the inertia of the balance wheel and the energy storedin the hairspring, the impulse pin enters the fork slot of the leverduring its return, rotating said lever and unlocking the lever palletfrom the escape wheel tooth. When the unlocking action is completed, theescape wheel, driven by the mainspring and gear train, rotates, forcingthe lever pallet outward thereby again pivoting the lever. The oppositeside of the fork slot on the pivoting lever then strikes the oppositeside of the impulse pin, causing the balance wheel to rotate andincrease tension of the hairspring in the opposite direction. Theopposite lever pallet at this time, locks another escape wheel tooth andthe lever is now positioned for entry of the impulse pin in the oppositedirection. As long as power is transmitted to the escape wheel, thesequence described continues to cycle.

The type escapement described is the commonly known detached leverescapement, where the balance is free of the influence of the escapementand power from the gear train, except during unlocking and impulse. Thelever is positioned for repeated entry and re-entry of the impulsemember into the forked end of the escapement lever. If the timepiece andconsequently the movement is subjected to an external shock, theescapement lever may be jolted away from its banking position at acrucial time during balance wheel oscillation, when the impulse memberis out of the fork slot of the lever, and cause lock-up of the movement.To insure entry of the impulse pin into the lever fork, the motion ofthe lever away from the banking during shocks is limited by theinteraction of the guard pin and safety rolli The lock remains betweenpallet and escape wheel and is commonly referred to as guard pin safetylock.

In light of the above, the principal object of the present invention isto provide an improved timepiece escapement mechanism that features anextremely efficient escapement control element in the form of acombination safety roll and impulse member that is simple inconstruction, very inexpensive to manufacture, is easy to install,requires no adjustment, is very durable in use and has very lowcoclficient of friction. In prior and current escapements of the typedisclosed herein, the impulse pin must necessarily be lubricated toreduce the ing the problem of adhesion.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged schematicperspective view of the escapement mechanism of a timepiece showing thenovel combination safety-roller impulse member of the present invention;

FIG. 2 is similar to FIG. 1 but shows the safety roller and impulse pinarrangement so well known in the prior art;

FIG. 3 is a perspective view of the combination safety roller impulsemember of FIG. 1;

FIG. 4 is greatly enlarged front elevational view thereof; and

FIG. 5 is a sectional view taken along lines 5 5 of FIG. 4.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to FIG. 1 of thedrawing, there is shown an escapement comprising an escape lever 10 andan escape wheel 12 which form the basic portion of a clock or watchescapement. The escape lever is mounted on an escape lever shaft 14which is journaled in the base plates (not shown) of the movement. Theescape wheel 12 is mounted on an escape wheel shaft 16, one end of whichis also joumaled in the base plates. The toothed end of shaft 16 isdriven by the main spring of the movement by means of the gear train,the operation and characteristics of which are very well known andtherefor not disclosed herein. The escape lever 10 carries a pair ofpallet pins 20 which alternately engage the teeth 24 of the escape wheel12 and effect the impulsing and locking operations that result in aunidirectional rotation of the escape wheel 12. If the escape wheel 12is not periodically locked, the main spring will rotate the gear trainat full speed until the main spring is completely unwound. The escapewheel is prevented from such free rotation by the action of the escapelever 10 which includes a fork-like portion 26 at one end thereof.

In the prior art, shown in FIG. 2, the opening formed by the times ofthe fork, is adapted to fit over an impulse pin 30, which is usually ofhardened steel or a jewel and is fixed adjacent the hub of a balancewheel 32 in a well-known manner. Roller 34, commonly known as the safetyroller and customarily of brass, is secured fast to a balance wheelstaff 36 by pinning or the like. An indented crescent 38 of the safetyroller allows the roller to pass under the urge of a hairspring 40 whenthe escape lever 10 is unlocked. The movement of the lever by theimpulse pin is made at the fork; the impulse pin enters the fork openingand unlocking and impulse are effected. As one tooth slides off theimpulse plane of one of the pallet pins, another tooth is stopped by theother pallet pin. During the stopping of the escape wheel, the balancewheel 32 continues to rotate; impulse pin 30 is then completely free ofthe fork-like portion 26. During the circular motion of the balance, thehairspring 40 has been wound up" until it has stopped the balance andreversed its motion. The impulse pin 30 then returns to the forkopening, strikes a fork tine and pivots lever 10 whereupon the escapewheel 12 is unlocked. The sliding of a tooth 24 on the other pallet sobegins again and the cycle continues. Thus the motion of the balancewheel 32 is maintained by the locking and unlocking action to generateimpulses. Guard pin 42 is fixed at the forked end of escape lever 10 andaligns with crescent 38 during the unlocking and impulse functions ofthe escape lever. During the remainder of the oscillatory excursion ofthe balance wheel the guard pin 42 serves to prevent unlocking of theescapement lever 10 and thereby guards against malfunction of thecoefficient of friction during unlocking. However, lubricationescapement mechanism.

According to the present invention, a simple one-piece roller andimpulse member is generally designated 44 and is provided with animpulse portion 46 and a safety roller portion 48. The composite unit 44is preferably of a durable plastic such as DELRIN, for one example, andis formedas shown in the drawings. The impulse portion 46 is providedwith a fork engaging extension 50 having rounded edges 52 whichcontribute to the smooth operation of the escapement by rolling in andout of contact with the tine 28. Due to the character of the plasticmaterial, application of lubrication between parts is unnecessary.

To insure that the all-important concentricity of the safety rollerportion 48 is preserved, and also to facilitate assembly, the safetyroller portion is provided with a complete opening 54 or poising slotfor accomodating the guard end of guard pin 42 in distinction to thenotch 38 of the prior art FIG. 2. The poising slot 54 is aligned withthe fork-engaging extension 50, as best seen in FIG. 4.

It is important to note that a bore 56 in impulse portion 46 is oflesser diameter than the semi-circular base 58 of the opening 54 insafety roller portion 48. Reference is made to the zone designated Wwhich is of lesser diameter than the zone designated V in FIG. 5.

Accordingly, in assembling the composite one piece roller and impulsemember, the bore 56 is entered on the balance staff and the compositeunit is positioned by force-fitting, completely independent of thebalance wheel. Assembly is greatly facilitated by obviating independentand critical alignment of impulse pin and safety roller which washeretofore the practice.

From the foregoing description it may be readily ascertained that theinvention may be readily and reliably reproduced and assembled at a veryhigh production rate and with attendant low manufacturing costs.

What is claimed is:

1. ln a timepiece having a driven escape wheel with evenly spaced teethabout the periphery thereof, a two-ended escape lever pivoted betweenits ends, the escape lever having pallets at one end engaging the teethof the escape wheel and a fork at its other end, a guard pin also at theother end of the escape lever adjacent the fork, a balance staffimpulsed in a first direction by the fork of the escape lever throughthe driven teeth of the escape wheel, a hairspring connected to thebalance staff to drive same in a direction opposite the impulsed firstdirection following an impulse imparted by the fork of the escape lever,the improvement comprising a composite impulse member and safety rollerformed of durable plastic and force-fitted on the balance staff inoperative relation to the fork and guard pin of the escape lever totimingly control the drive of the escape wheel, said impulse memberhaving an impulse portion integral therewith and said safety rollerhaving a slotted portion therein, the impulse and slotted portions beingformed in the same axial plane to operatively cooperate with the forkand guard pin, respectively, of the escape lever, and means integralwith said impulse member and safety roller for maintaining theconcentricity of the safety roller during the force-fitting of thecomposite impulse member and safety roller on the balance staff.

2. The composite impulse member and safety roller of claim 4 whereinsaid means for maintaining the concentricity of said safety rollercomprises, the impulse member having bore therethrough and the safetyroller slotted portion having a substantially semi-circular base portionon the same axis of the bore as the impulse member, the bore in theimpulse member being of smaller diameter than the semi-circular bore inthe safety roller, whereby the concentricity of the safety roller ispreserved during force fitting of the composite impulse member andsafety roller on the balance staff.

i t 4 t i

1. In a timepiece having a driven escape wheel with evenly spaced teethabout the periphery thereof, a two-ended escape lever pivoted betweenits ends, the escape lever having pallets at one end engaging the teethof the escape wheel and a fork at its other end, a guard pin also at theother end of the escape lever adjacent the fork, a balance staffimpulsed in a first direction by the fork of the escape lever throughthe driven teeth of the escape wheel, a hairspring connected to thebalance staff to drive same in a direction opposite the impulsed firstdirection following an impulse imparted by the fork of the escape lever,the improvement comprising a composite impulse member and safety rollerformed of durable plastic and force-fitted on the balance staff inoperative relation to the fork and guard pin of the escape lever totimingly control the drive of the escape wheel, said impulse memberhaving an impulse portion integral therewith and said safety rollerhaving a slotted portion therein, the impulse and slotted portions beingformed in the same axial plane to operatively cooperate with the forkand guard pin, respectively, of the escape lever, and mEans integralwith said impulse member and safety roller for maintaining theconcentricity of the safety roller during the force-fitting of thecomposite impulse member and safety roller on the balance staff.
 2. Thecomposite impulse member and safety roller of claim 4 wherein said meansfor maintaining the concentricity of said safety roller comprises, theimpulse member having bore therethrough and the safety roller slottedportion having a substantially semi-circular base portion on the sameaxis of the bore as the impulse member, the bore in the impulse memberbeing of smaller diameter than the semi-circular bore in the safetyroller, whereby the concentricity of the safety roller is preservedduring force fitting of the composite impulse member and safety rolleron the balance staff.